Adaptive synchronization of chaotic Colpitts circuits against parameter mismatches and channel distortions

In this work, synchronization of chaotic Colpitts circuits, using adaptive controllers to combat circuit parameter mismatches and channel distortions, is studied by numerical simulations. Synchronization errors caused by different main circuit components are compared, and compensation for time-constant and time-varying circuit parameter mismatches is demonstrated. Different kinds of channel distortions, including time-constant and time-varying channel attenuation, Additive White Gaussian Noise (AWGN) are all investigated by numerical simulations and discussed. Simulation results indicated that the synchronization performance of chaotic Colpitts circuits can be greatly improved by applying adaptive controllers when parameter mismatches and channel attenuation are considered as time-constant or time-varying, but have no obvious enhancements regarding the effect on AWGN channel.     

印第安纳波利斯儿童博物馆的场景式项目学习

印第安纳波利斯儿童博物馆基于美国K-9国家课程标准,开发了几十门项目学习课程,根据项目学习原则布置各个场景,为家长、学校、学生提供真实化情境、问题化引导、职业化体验的"Hands on"式教育。     

Dependence of nucleotide physical properties on their placement in codons and determinative degree

INTRODUCTION It is well-known from the genetic code structure that there exists a connection between codons and physical and chemical amino acid properties (Lewin, 1983). Codon properties in turn are defined by physical properties of the nucleotides from which they are compounded (Ratner, 1985; 2000). The most important properties of nucleotides as complex three-dimensional molecules are their dipole moment, heat of formation and energy of the most stable con- formation (Schneider and Be…     

论中国西部粮食安全的思路与对策

西部大开发 ,一退三还 ,使得本来粮食短缺、经济落后的西部地区粮食安全雪上加霜 ,进而成为中国粮食安全的隐患。本文认为解决西部粮食安全的思路在于走区域大循环之路 ,并从粮食流通体制、提高粮食自给率、增加稳定的供应和提高西部农民购买力等方面采取对策 ,以实现西部和全国粮食安全的良性循环和可持续发展。     

大学生创造能力测试与培养

１９９７年我院承担了山西省“理工科大学生创造能力培养与实践”的科研课题，课题组分别于１９９９年和２０００年对同一人群进行了创造力的对比测试。 １、首次测试结果和分析 １９９９年３月，课题组参考日本学者稻田享太的创造性素质测试题，设计了适合中国理工科大学生的试卷，随机抽取四个班１００名学生进行创造能力测试，结果如表１所示。 以创造能力的分值为横坐标、每一分数段的学生人数为纵坐标，可以绘制如图１所示的创造能力得分分布。 从图１可见，曲线的峰值位于１４～１９分之间，１００名学生的平均得分为１８．９２分，评…     

On group and phase velocities manifested through exact solutions to the equations of some propagation phenomena

A system of non-Hermite, non-orthogonal functions that are new for concrete applications is introduced to generate explicit and previously unknown, physically meaningful solutions for bar and plate equations. The approach allows in some cases to establish completeness of these sets of solutions. Various other separate results technically related to these basic development are presented. In the available literature there are no registered efforts to extract the two velocities from exact solutions of the equations of the processes in which the two parameters are explicitly present.     

一种有效缓解数据稀疏问题的协同过滤推荐算法

传统协同过滤推荐算法依据共同评分项目计算用户相似度, 进而产生推荐项目。然而, 随着用户和商品数量的不断增加, 用户共同评分的项目会越来越少, 甚至没有, 因此传统协同过滤推荐算法对用户之间相似度的衡量将会越来越不准确, 从而影响推荐系统的性能。针对这一问题, 本文对用户相似度的计算方法进行了改进, 提出直接相似度和间接相似度的概念, 同时引入关键人物权重, 进一步提高推荐系统的准确性。     

OpenURL框架结构分析

OpenURL作为一种开放式链接框架结构，与传统信息链接框架相比，增加了许多新的功能，成为信息资源整合的重要工具，受到图书情报界的密切关注，也将被美国全国信息标准组织(NISO)所接收。本文在分析OpenURL框架结构和运行机制的基础上，讨论其在信息资源整合中的使用。     

推进农村工业化与城镇化的协调互动发展

农村工业化和城镇化,是解决“三农”问题的两个重大战略,二者又是互相影响、相互制约的。本文分析了推进农村工业化与城镇化的协调互动发展的必要性,并对当前未能有效实现二者协调发展的原因进行了探讨,最后从理论认识和政策制度等方面提出推进农村工业化与城镇化协调互动发展的对策建议。